1. Field of the Invention
The present invention relates to a digital image stabilization technique and, more particularly, to a digital image stabilization method that integrates a digital image stabilization algorithm and a digital video coding system and makes use of motion vectors generated through motion estimation in the digital video coding system for stabilization.
2. Description of Related Art
With the development of multimedia technology, digital still cameras and camera phones are utilized by more and more consumers. Compact, portable and multifunctional digital products are critical features in order to ensure success in the market. Although consumers desire miniaturized multimedia products, they also demand pictures of high quality. Digital cameras and cellular phone cameras, however, easily take poor quality pictures due to shaking or slight hand movement which produces annoying jerky image motion.
Both the digital video coding system and the digital stabilization algorithm need to make motion estimation to determine the motion vector of each frame. In processing digital video coding and stabilization, when one frame enters the system, the motion vector is first calculated to achieve the object of stabilization. Next, the frame is compressed. Because both stabilization and compression are required for each frame, various steps are performed to extract the motion information from the video signal in order to calculate the motion vector of frame. The amount of computation thus is relatively large.
In “digital image stabilization method and device” of Taiwan Publication No. I272550 disclosed on Feb. 1, 2007, a digital stabilization algorithm and a digital video coding system are integrated. Frames with jerky image motion in an image sequence are compensated, and the processing of I frames and P frames is emphasized. As shown in FIG. 1, after the I0 frame is compressed, the motion vector of the whole frame is obtained. The background region BR0 in the I0 frame is compared, and this motion vector is used to adjust the P1 frame for stabilization. Making use of this image processing method, when a frame enters, it is not necessary to calculate the motion vector of the whole frame. Instead, the motion vector of the preceding frame obtained during compression is used to estimate the motion vector of the current frame. This method, however, can only be applied to the processing of the I frame and P frame.
The present invention discloses a digital image stabilization method of B frames to remove unwanted motion in the image sequence while preserving intentional camera movement so as to solve the above problems in the prior art.